Pathlight 2022 Prelim 4E Computing_P1 ANSWERS

4E Computing Paper 1 PRELIM 2022 1 2022 PRELIMINARY EXAMINATION Secondary 4 Express Computing Paper 1 ANSWERS AND MARKING SCHEME 1 (a) data corruption Data corruption occurs when computer data is made unusable by errors or alterations. [1] (b) any three: • Human error • Power failure • Hardware failure or damage • Malicious software [3] (c) perform regular backups [1] 2 (a) A316 = 1010 00112 = 1 x 27 + 1 x 25 + 1 x 21 +1 x 20 [1] = 128 + 32 + 2 + 1 = 16310 [1] (b) 10110112 = 1 x 26 + 1 x 24 + 1 x 23 + 1 x 21 +1 x 20 [1] = (64 + 16 + 8 + 2 + 1)10 = 9110 [1] (c) 10510 = 26 + 25 + 23 + 20 [1] = 0110 10012 (must be 8 bits) [1] 0 1 0 1 1 0 1 1 0 1 1 0 1 0 0 1

4E Computing Paper 1 PRELIM 2022 2 3 (a) Cell Data type A1 Text A2 Date B3 Currency F1 Percentage [4] (b) G8 =SUM(B2:B6) [2] (c) SUMIF(C2:C6,”Yes”,B2:B6) [1] The function is entered with 3 arguments, first the range where the criteria is contained is selected, then the criteria is entered, in this case “Yes”, then the sum range of cell is selected. The function then returns the sum of the corresponding cells that meet the criteria, in this case, cells B3:B4. [2]

4E Computing Paper 1 PRELIM 2022 3 4 Security Threat Description [6] Cookie A computer program that pretends to be a harmless file or useful application Pharming Phishing Spamming A small file used by websites to store personal information on a user’s web browser A computer program that attaches itself to a normally harmless program and modifies it The use of emails and fake websites that appear to be from reputable companies in order to steal personal information such as passwords and credit card numbers from users The use of data owned by someone by someone else, such as an intruder, without permission Trojan Horse The mass distribution of unwanted messages or advertising to email addresses collected from sources such as public mailing lists, social networking sites, company websites and blogs Virus The interception of requests sent from a computer to a legitimate website and redirection to a fake website to steal personal data or credit card details

4E Computing Paper 1 PRELIM 2022 4 5 (a) 5 marks for correct logic gates used, 1 mark for correct output. [6] 5 (b) 4 marks for correct output for X (1 mark for each pair of correct output). [4] A B C Working Space R S T U V X 0 0 0 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 1 0 1 1 0 1 1 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 0 1 0 1 0 0 0 0 1 1 0 1 1 1 1 1